Condensation polymerization methods use high temperatures, high vacuum and metal catalysts that are toxic. In particular, the preparation of polymers by condensation polymerization methods takes several days, and relies on high temperatures (T>200° C.) and low pressures (p<1 mmHg) to drive the polymerization to completion. As condensation polymerization methods operate at temperatures of greater than 200° C. and many photochromic compounds degrade above temperatures of 150° C., condensation polymerization methods can lead to degradation of photochromic compounds and are not suitable to produce photochromic polyesters. Additionally, condensation polymerization methods are not suitable for polymerizing lactones.
What is desired is a method for producing photochromic polyesters that are achieved by relatively low temperatures and would therefore minimize photochromic compound degradation. Such a result is particularly desirable given the high cost of photochromic compounds. Furthermore, biodegradable polyesters for biomedical applications that are free of toxic catalysts are highly valuable but are difficult to produce.